JP2000331375A - Near-field light recording/reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve recording density by irradiating a substrate changed from an opaque state to a transparent state with temperature by the light beam wherein light from a light source is focused with a focusing lens. SOLUTION: When a near-field light generating part 13 is irradiated with a laser beam, the distribution of temperature according to the distribution of beam intensity is produced on the surface. At this time, the light beam is transmitted only by the periphery around the center of the optical axis becoming transparent and becoming a critical temperature using the thin film of the near-field light generating part 13 as a substance whose transmitivity is changed by the beam temperature. That is, the light beam transmits a thermal aperture part 17 becoming the critical temperature or more and becoming transparent, and a small spot for the near-field light 18 is obtained as the gap (g) wherein the interval between the near-field light generating part 13 and a disk 2 is smaller than an incident light beam wavelength. And since a phase transition thin film 22 for recording formed on the surface of a disk substrate 21 is irradiated with the near-field light 18 of the small spot, high density recording for one bit information 23 is allowed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-density near-field (near-field) optical recording / reproducing apparatus capable of remarkably increasing the recording density by overcoming the diffraction limit of light.

[0002] Generally, the technology for recording optical information is CD, DV.
It has developed epoch-making mainly in D technology. In particular, the realization of the semiconductor blue light laser enables the recording density to be three to four times as high as that of the conventional red light laser, thereby realizing a large capacity optical recording technology.

[0003] However, recently, clearer image information has been demanded, and with the development of personal information terminals, there has been an increasing demand for smaller and lighter, larger-capacity information recording devices. For that purpose, a dramatic increase in information recording density is required.

Conventionally, as a large-capacity information recording device, a magnetic information recording device such as a hard disk used as an auxiliary storage device of a computer is known. The recording density of this apparatus has been improved by various technical improvements. On the other hand, as a recording apparatus that does not use magnetism, an optical recording medium using laser light is known. A recording device using magnetism has a limit in increasing the recording density as compared with an optical recording medium using a focused laser beam, and an optical recording medium is currently advantageous for realizing a large capacity.

However, also in this optical recording technology, theoretically, the recording density has a limit depending on the wavelength of a laser light source used for recording / reproducing.

In the optical recording technology, the minimum length of one bit of a data mark is determined by the following equation. d = [lambda] / (2NA) where [lambda] is the wavelength of light. The current semiconductor red light laser has a value of about 650 nm, and the blue light laser has a value of about 410 nm. NA is a numerical aperture, and a general optical lens is about 0.5 to 0.7. Therefore,
The minimum pitch between the identifiable data tracks is about the size of the light wavelength, and the length of the light wavelength is a limit for increasing the recording density. This limit is due to the property that light is diffracted, and a near-field (near-field) optical recording technique has recently been spotlighted as a technique for overcoming this.

In the near-field optical recording technique, a probe that transmits light within a light wavelength is approached, and light is input and output through the probe so as to exceed a spatial resolution limit limited by the light wavelength. Is the way.

[0008] As a method for realizing this, the technology which is currently closest to commercialization is US Terastor.
Solid immersion lens (SIL: solid
immersion lens). This method uses S
The NA value is increased by using IL to reduce the focal point of a laser beam used for recording / reproducing, thereby improving the spatial resolution due to the diffraction limit of light.

This method is advantageous for commercialization because a conventional optical recording / reproducing method using a normal lens can be used. However, even when SIL is used, the NA value is limited, so that there is still a limit in increasing the recording density.

In addition to the above-described method, a near-field scanning optical microscope (NSOM) using a near-field probe method in which an optical fiber probe (optical fiber probe tip) is brought close to within a recording / reproducing light wavelength.
oscopy), but it is difficult to maintain a constant distance between the optical fiber probe and the disk in the near-field range, and due to technical problems such as low data recording / reproduction speed,
It is not used in information recording devices.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems by providing a near-field optical recording / reproducing apparatus capable of further improving the recording density by using a near-field optical recording technique. .

[0012]

The near-field optical recording / reproducing apparatus according to the present invention is characterized by using a substance which changes from an opaque state to a transparent state depending on temperature. That is,
The light from the light source is focused by a focusing lens, the focused light is irradiated on the substance, and the high temperature of the focused light beam is utilized by utilizing the fact that the center of the focused light is higher in temperature than other parts. It is characterized in that the light is radiated to the disk only through the central part.

The substance whose transmittance changes depending on the temperature is to be formed from any one of VO ₂ , Sb and AgO _X.

Still another feature of the present invention is that the light generated from the light source is reflected by a mirror and guided to a focusing lens, and the focusing lens and the substance are protected by a package housing.
The mirror and the package housing are supported by a support,
It is also characterized in that the support is attached to the tip of a cantilever connected to the actuator.

Still another feature of the present invention is that an optical fiber or a lens is formed between the light source and the mirror to transmit light generated from the light source to the mirror.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A near-field optical recording / reproducing apparatus according to the present invention having the above features will be described below with reference to the accompanying drawings. First, the present invention generates near-field light using a thermal opening made of a substance whose transparency changes with temperature, and realizes the size of a data mark equal to or smaller than the wavelength of an input laser beam using the near-field light. is there. The position between the data track pitches is adjusted by a cantilever connected to the fine adjustment actuator.

FIG. 1 is a view showing a near-field optical recording / reproducing apparatus having a thermal opening according to an embodiment of the present invention, and FIG. 2 is a sectional view of the optical information signal pickup head of FIG.
The structure of the present embodiment basically includes a cantilever 1 connected to an actuator for fine position adjustment and a laser diode integrated with the cantilever 1, as shown in FIGS. Mirror mount 11 connected to cantilever 1
And a 45 ° mirror 15 formed on the mirror mount 11, a converging lens 12, a near-field light generator 13 made of a thin film for generating a thermal aperture 17, and protecting the near-field light generator 13. Housing 16 for
It is composed of

An optical fiber 14 or a lens (not shown) for transmitting a laser beam generated from the laser diode to the 45 ° mirror 15 is disposed between the laser diode and the 45 ° mirror 15. That is, light from a light source (not shown) is guided to the mirror 15 by the optical fiber 14, and is guided to the near-field light generating unit 13 by an optical path focused by the focusing lens 12.

The laser beam generated from the laser diode reaches the 45 ° mirror 15 via the optical fiber 14 or the lens, and then is almost 9 ° by the 45 ° mirror 15.
The light is reflected at an angle of 0 °, is focused by the focusing lens 12, and passes through the near-field light generating unit 13. Near-field light generator 1
The laser beam transmitted through the optical disk 3 reaches the optical disk 2 to record / reproduce information. Here, the near-field light generating unit 13 is made of a material having a characteristic of changing from opaque to transparent depending on the temperature.

As this kind of substance, a VO ₂ thin film, a Sb thin film, AgO _X or the like can be used. VO ₂ thin film is about 60 ~
It has a property of causing a metal-insulator transition between 70 ° C. and not transmitting light below that temperature and transmitting light above that temperature (Hiroyuki Abe et al., Jpn. J. Appl. Phys.
vol. 36, pp. 165-169, 1997). The Sb thin film is about 2
It has the property that light transmittance increases at about 00 ° C. (J. Tominaga et al, Applied Physics Letters, vol.
73, no. 15, p2078).

The principle of generating the thermal aperture 17 of the near-field light generator 13 using the optical properties of such a substance will be described with reference to FIG.

As shown in FIG. 3, when the near-field light generating unit 13 is irradiated with a laser beam, the surface of the material irradiated with the laser beam corresponds to the intensity distribution of the laser beam due to the light intensity distribution of the laser beam. A temperature distribution is generated. At this time, since the light transmittance of the thin film of the near-field light generating unit 13 changes depending on the temperature, the light transmittance partially changes depending on the temperature of the laser beam. That is, a portion around the center of the optical axis having a temperature at which it becomes transparent, that is, a temperature equal to or higher than the critical temperature T _C (a radius of d in FIG. 3).
Only transmit light. In short, only the transparent part transmits light. The laser beam transmitted by the transparent portion can be reduced to below the limit (shown by D in the figure) of the size of the light spot that can be realized by the general optical system.

The laser beam reduced by the thermal aperture 17 of the near-field light generating section 13 becomes a near-field light 18 as shown in FIG. And the 1-bit information 23 is recorded or reproduced. The near-field light 18 is generated because the distance between the near-field light generating unit 13 and the surface of the disk 2 maintains a gap g smaller than the wavelength of the incident light. Therefore, in this embodiment, in order to maintain the gap g smaller than the wavelength of the incident laser beam, the aerodynamic levitation method (aerody
namically levitation). Therefore, the focusing lens 12 and the near-field generating unit 13 are arranged at the tip of the cantilever.

An information recording and reproducing method of the near-field optical recording / reproducing apparatus according to the present embodiment having the above characteristics will be described below. First, as shown in FIG. 1, in order to record information at a desired position on the disk 2, the optical pickup head shown in FIG. 2 is moved using the cantilever 1 connected to the actuator.

Next, when the optical pickup head reaches a desired position, a recording laser beam is generated from the laser diode, and this laser beam reaches the 45 ° mirror 15 via the optical fiber 14 or the lens. The laser beam is reflected by the 45 ° mirror 15 and is focused by the focusing lens 12 on the near-field light generator 13.

As shown in FIG. 3, only a portion of the laser beam having reached the near-field light generating section 13 having a temperature equal to or higher than the critical temperature T _C passes through the thermal opening 17 of the near-field light generating section 13. It becomes the near-field light 18. Since the near-field light 18 is light that transmits only a part of the converged light beam as described above, it becomes a very small spot. The near-field light formed as the small spot is irradiated on the recording thin film formed on the surface of the disk substrate 21.
Bit information 23 can be recorded at high density.

Next, the actuator is finely adjusted and the pickup head is moved to a desired position to continuously record information.

Here, the minimum resolution that can be distinguished in the present embodiment depends on the minimum movement distance of the position fine adjustment actuator, and the minimum movement distance can be controlled within about 0.1 μm.

Since the method of reproducing the recorded information is not particularly different from the recording method, the description is omitted.

[0030]

As described above, according to the near-field optical recording / reproducing apparatus of the present invention, the thermal aperture is formed by utilizing the heat of the light beam itself irradiated for recording / reproducing. Since near-field light passing through the opening is generated and recording / reproducing is performed using the near-field light, the size of a data mark smaller than the wavelength of the input laser beam can be realized. Therefore, the recording density can be remarkably increased by overcoming the diffraction limit of light. Further, since the position between data track pitches is adjusted by the cantilever connected to the fine adjustment actuator, the recording density can be further improved.

It will be obvious to those skilled in the art that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be limited only by the appended claims.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a near-field optical recording / reproducing apparatus having a thermal opening according to an embodiment of the present invention.

FIG. 2 is a structural sectional view showing the optical pickup head of FIG. 1;

FIG. 3 is a diagram illustrating a principle of generating a thermal aperture of the near-field light generating unit in FIG. 2;

FIG. 4 Generation of near-field light and information recording /
The figure which shows a reproduction | regeneration principle.

[Explanation of symbols]

 1: cantilever 2: disk 11: mirror mount 12: focusing lens 13: near-field light generator 14: optical fiber 15: 45 ° mirror 16: package housing 17: thermal aperture 18: near-field light 21: disk substrate 22 : Phase transition thin film 23: 1 bit information

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G11B 7/09 G11B 7/09 D (72) Inventor John Wook Boo Republic of Korea Shi Pundang-Chong Chongja-Dong (No address) Hansol Dugong Apartment 510-1501 (72) Inventor Chor Park South Korea 14-4 ・ Shimmijo Apartment ・ 102-1403

Claims (9)

[Claims] A light source for generating light; a converging lens for converging light generated from the light source; a near-field generating unit made of a substance whose light transmittance changes according to temperature; And an optical path for guiding to a near-field generator.
Playback device. 2. The near-field optical recording / reproducing apparatus according to claim 1, wherein the light source is a laser diode. 3. A mirror for reflecting the light generated from the light source to the focusing lens, a package housing for protecting the focusing lens and the near-field generating unit, and a support for supporting the mirror and the package housing. 2. The near-field optical recording / reproducing apparatus according to claim 1, further comprising: 4. The near-field optical recording / reproducing apparatus according to claim 3, further comprising a cantilever connected to the support and moving the support. 5. The apparatus according to claim 4, wherein the cantilever is connected to an actuator and is finely adjusted in position.
3. The near-field optical recording / reproducing apparatus according to claim 1. 6. The near-field optical recording / reproducing apparatus according to claim 4, wherein the light source is located on the cantilever. 7. The near-field optical recording / reproducing apparatus according to claim 3, wherein the mirror is a 45 ° mirror. 8. The near field according to claim 3, wherein one of an optical fiber and a lens is formed between the light source and the mirror so that light generated from the light source is transmitted to the mirror. Optical recording / reproducing device. 9. The near-field generator includes VO ₂ , Sb, Ag.
O near field optical recording / reproducing apparatus according to claim 1, characterized in that it consists of one of _X.